SEOUL, June 4 (Yonhap) -- North Korea said Monday its military has entered map coordinates of some conservative South Korean media as it threatened to strike their headquarters for their alleged insult to North Korea's new leader Kim Jong-un.

General Staff of the Korean People's Army said its troops have targeted the Seoul headquarters of the Chosun Ilbo, the Joongang Ilbo, the Dong-A Ilbo newspapers as well as KBS, MBC and SBS television stations and CBS radio.

"We would like to ask the Lee group if it wants to leave all this to be struck by the (North) or opt for apologizing and putting the situation under control, though belatedly," the General Staff said in an English-language ultimatum, referring to South Korean President Lee Myung-bak.

Seoul, the South Korean capital city of more than 10 million people and home to the South Korean media, is within range of North Korea's artillery.

"If the Lee group recklessly challenges our army's eruption of resentment, it will retaliate against it with a merciless sacred war of its own style as it has already declared," the General Staff said in the ultimatum carried by the North's official Korean Central News Agency.

It also warned that the North is "fully ready for everything" and "time is running out."

The latest threat came in response to some South Korean media reports critical of the North's celebration of the Korean Children's Union under way in Pyongyang.

About 20,000 North Korean children have pledged their allegiance to Kim as the North began a six-day festival on Sunday marking the 66th anniversary of the Korean Children's Union, according to Pyongyang's state media.

Some South Korean media dismissed the celebration as part of the North's attempt to win support for Kim, who took over the country following the December death of his father, the long-time leader Kim Jong-il.

Channel A, a television arm of the Dong-a Ilbo newspaper, has likened Kim to the late German dictator Adolf Hitler over the anniversary celebration of the Korean Children's Union.

The North has long bristled at any outside criticism of its leader and has made similar threats against the South over the past several months, although no actual attack has occurred yet.

South Korea has repeatedly vowed to avenge any North Korean attacks following the North's two provocations in 2010 that killed 50 South Koreans, mostly soldiers.